Control chip for touch panel with high sensitivity and operating method thereof

ABSTRACT

There is provided a capacitive touch device including a touch panel and a control chip. The touch panel includes a detection electrode configured to form a self-capacitor. The control chip includes an emulation circuit and a subtraction circuit. The emulation circuit is configured to output a reference signal. The subtraction circuit is coupled to the emulation circuit and the detection electrode, subtracts the reference signal outputted by the emulation circuit from a detected signal outputted by the detection electrode to output a differential detected signal, and identifies a touch event according to an amplified differential detected signal so as to improve the touch sensitivity.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation application of U.S. application Ser. No. 15/080,718, filed on Mar. 25, 2016, which claims the priority benefit of Taiwan Patent Application Serial Number 104109783, filed on Mar. 26, 2015, the full disclosure of which is incorporated herein by reference.

BACKGROUND 1. Field of the Disclosure

This disclosure generally relates to a touch device, more particularly, to a capacitive touch device with high sensitivity and an operating method thereof.

2. Description of the Related Art

Because a user can operate a touch panel by intuition, the touch panel has been widely applied to various electronic devices. In general, the touch panel is classified into capacitive, resistive and optical touch panels.

The capacitive touch sensor is further classified into self-capacitive touch sensors and mutual capacitive touch sensors. These two kinds of touch sensors have different characteristics of the capacitive variation, so they are adaptable to different functions. For example, the mutual capacitive touch sensors are adaptable to the multi-touch detection, and the self-capacitive touch sensors have a higher sensitivity to hovering operations and a lower sensitivity to water drops. However, how to improve the touch sensitivity of these two kinds of capacitive touch sensors is an important issue.

SUMMARY

Accordingly, the present disclosure provides a capacitive touch device with high sensitivity and an operating method thereof.

The present disclosure provides a capacitive touch device and an operating method thereof in which an emulation circuit is arranged in a control chip to generate a reference signal as a cancellation of a detection signal, and thus a size of a detection capacitor in the control chip is reduced.

The present disclosure provides a capacitive touch device and an operating method thereof in which an emulation circuit is arranged in a control chip to generate a reference signal as a cancellation of a detection signal, and thus a touch sensitivity is improved.

The present disclosure provides a control chip for a touch panel. The touch panel includes a detection electrode configured to form a self-capacitor. The control chip includes an input resistor, an amplifying circuit and an emulation circuit. The input resistor is configured to be coupled to an output end of the detection electrode. The amplifying circuit is connected with the input resistor. The emulation circuit is configured to directly receive a drive signal and not connected to the output end of the detection electrode. The input resistor and the amplifying circuit are configured to form a first filter circuit with the self-capacitor. The emulation circuit is configured to form a second filter circuit. The frequency response of the second filter circuit is determined according to a frequency response of the first filter circuit.

The present disclosure further provides a control chip for a touch panel. The touch panel includes a plurality of detection electrodes respectively configured to form a self-capacitor. The control chip includes an emulation circuit, a plurality of programmable filters and a subtraction circuit. The emulation circuit is not connected to signal outputs of the detection electrodes and configured to directly receive a drive signal and output a reference signal. The plurality of programmable filters is respectively coupled to the signal outputs of the detection electrodes. The subtraction circuit is directly connected to the emulation circuit, and configured to be sequentially coupled to the programmable filters in a self-capacitive mode, and perform a differential operation on the reference signal outputted by the emulation circuit and a detection signal outputted by the coupled programmable filter to output a differential detected signal.

The present disclosure further provides an operating method of a control chip for a touch panel. The touch panel includes a plurality of drive electrodes and a plurality of receiving electrodes extending along different directions. The control chip includes an emulation circuit, a plurality of detection capacitors, a subtraction circuit and an anti-aliasing filter. The operating method includes the steps of: respectively coupling, in a self-capacitive mode, a first drive signal to first ends of the drive electrodes via the detection capacitors and respectively coupling the subtraction circuit to second ends of the drive electrodes; directly inputting, in the self-capacitive mode, another drive signal to the emulation circuit, which is not connected to the second ends of the drive electrodes, to output a reference signal; and respectively coupling, in a mutual capacitive mode, the first drive signal to the first ends of the drive electrodes without passing the detection capacitors, and respectively coupling the anti-aliasing filter to second ends of the receiving electrodes without passing the subtraction circuit.

A capacitive touch device of the present disclosure is adaptable to a touch device which uses only a self-capacitive detection mode, and to a touch device which uses a dual-mode detection including the self-capacitive detection mode and a mutual capacitive detection mode.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects, advantages, and novel features of the present disclosure will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.

FIG. 1 is a schematic block diagram of a capacitive touch device according to one embodiment of the present disclosure.

FIG. 2 is a schematic block diagram of a capacitive touch device according to one embodiment of the present disclosure.

FIG. 3 is another schematic block diagram of a capacitive touch device according to one embodiment of the present disclosure.

FIG. 4A is the waveform of a detection signal and a reference signal in the capacitive touch device of the embodiments of FIGS. 2 and 3.

FIG. 4B is a waveform of a differential detected signal of the detection signal and the reference signal in FIG. 4A.

FIG. 5 is a flow chart of an operating method of a capacitive touch device according to one embodiment of the present disclosure.

FIG. 6 is a frequency response of a filter circuit of a capacitive touch device according to one embodiment of the present disclosure.

DETAILED DESCRIPTION OF THE EMBODIMENT

It should be noted that, wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.

Please refer to FIG. 1, it is a schematic block diagram of a capacitive touch device according to one embodiment of the present disclosure. The capacitive touch device 1 includes a control chip 100 and a touch panel 13, wherein the capacitive touch device 1 is preferably able to detect by a self-capacitive mode. In some embodiments, the capacitive touch device 1 is able to detect approaching objects and distinguish touch positions by successively using a self-capacitive mode and a mutual capacitive mode. For example, in some embodiments, because a scanning interval of the self-capacitive mode is short, the capacitive touch device 1 is able to identify whether any object is approaching using the self-capacitive mode. After an approaching object is identified, a touch position is identified using the mutual capacitive mode. In other embodiments, the capacitive touch device 1 is able to identify a rough position of an approaching object and determine a window of interest (WOI) on the touch panel 13 with the self-capacitive mode, and then identify a fine position within the window of interest with the mutual capacitive mode to reduce data amount to be processed in the mutual capacitive mode. It should be mention that implementations of the self-capacitive mode and the mutual capacitive mode mentioned above are only intended to illustrate, but not to limit the present disclosure.

The touch panel 13 includes a plurality of detection electrodes 131 to respectively form a self-capacitor C_(s), wherein the detection electrodes 131 include a plurality of drive electrodes and a plurality of receiving electrodes extending along different directions, e.g., perpendicular to each other. Mutual capacitors C_(m) (referring to FIGS. 2 and 3) are formed between the drive electrodes and the receiving electrodes. The principle of forming self-capacitors and mutual capacitors in a capacitive touch panel is known and is not an object of the present disclosure, and thus details thereof is not described herein.

The control chip 100 includes a plurality of drive circuits 11, a plurality of detection capacitors C_(in) and an emulation circuit 150, wherein the emulation circuit 150 is used to emulate the characteristics of the detection line in a self-capacitive mode (described hereinafter). In the self-capacitive mode, the drive circuits 11 and the detection capacitors C_(in) are electrically coupled to signal inputs of the detection electrodes 131 via pins. The drive circuits 11 output a drive signal Sd, e.g., a sine wave, a cosine wave or a square wave to the detection electrodes 131. In a mutual capacitive mode, only the drive circuit 11 corresponding to the drive electrode outputs the drive signal Sd, whereas the drive circuit 11 corresponding to the receiving electrode is bypassed.

Please refer to FIG. 2, it is a schematic block diagram of a capacitive touch device according to one embodiment of the present disclosure. As mentioned above, the capacitive touch device 1 includes a touch panel 13 and a control chip 100. The control chip 100 includes a plurality of drive circuits 11, a plurality of detection capacitors C_(in), an analog front end 15 and a digital back end 16, wherein as the digital back end 16 is not an object of the present disclosure, details thereof are not described herein. In the present disclosure, the drive circuits 11 are able to be electrically coupled to signal inputs of the detection electrodes 131 via the detection capacitors C_(in) (e.g. in the self-capacitive mode) or bypassing the detection capacitors C_(in) (e.g. in the mutual capacitive mode), wherein said coupled to and bypassing the detection capacitors C_(in) is able to be implemented by arranging a plurality of switches SW₁ between the drive circuits 11 and the touch panel 13.

The analog front end 15 includes an emulation circuit 150, a plurality of programmable filters 151, a subtraction circuit 52, a gain circuit 153 and an anti-aliasing filter (AAF) 154. The programmable filters 151, the detection capacitors C_(in) and the self-capacitors C_(s) of the detection electrodes 131 form a first filter circuit, wherein the first filter circuit is, e.g., a band-pass filter (BPF) or a high-pass filter (HPF). The first filter circuit is able to further form a band-pass filter having a predetermined bandwidth with a low-pass filter formed by the anti-aliasing filter 154. In one embodiment, the signal output of each detection electrode 131 is coupled to (e.g. via a switch) one programmable filter 151. It should be mentioned that although only the horizontally arranged detection electrodes 131 shown in FIGS. 2 and 3 are coupled to the programmable filters 151, in other embodiments the programmable filters 151 are also coupled to the longitudinally arranged detection electrodes 131, and the present disclosure is not limited to those shown in FIGS. 2 and 3.

The emulation circuit 150 forms a second filter circuit and outputs a reference signal S_(ref), wherein the second filter circuit is, e.g., a band-pass filter or a high-pass filter. The second filter circuit is able to further form a band-pass filter having a predetermined bandwidth with a low-pass filter formed by the anti-aliasing filter 154. The subtraction circuit 152 is coupled to the emulation circuit 150 and is sequentially and electrically coupled to the programmable filters 151 via switches SW₂ in a self-capacitive mode to be further electrically coupled to the detection electrodes 131. The subtraction circuit 152 performs a differential operation on the reference signal S_(ref) outputted by the emulation circuit 150 and a detection signal S_(ol) outputted by the coupled programmable filter 151 to output a differential detected signal S_(diff). To be more precisely, in the present disclosure, the detection capacitors C_(in) are respectively and electrically coupled to signal inputs of the detection electrodes 131 via a plurality of switches (e.g. SW₁), and the subtraction circuit 152 is respectively and electrically coupled to the programmable filters 151 and the detection electrodes 131 via a plurality of switches (e.g. SW₂).

In the present disclosure, the detection capacitor C_(in) is disposed in the control chip 100 to form the voltage division with the self-capacitor C_(s). Accordingly, the capacitive touch device 1 identifies a touch event according to a variation of peak-to-peak values of the differential detected signal S_(diff), wherein the differential detected signal S_(diff) is a continuous signal. Before a touch event is identified, the differential detected signal S_(diff) is further filtered or digitized. For example, FIG. 2 shows the touched differential detected signal S_(touch) and the non-touched differential detected signal S_(non). However, as the self-capacitor C_(s) is generally very large, an effective voltage division is implemented by using a large detection capacitor C_(in). Therefore, the considerable disposition space in the chip for the large capacitor is necessary such that a total size of the control chip 100 is unable to be reduced.

Accordingly, in the present disclosure, the circuit characteristics of the detection line (e.g. from the drive circuit 11 via the detection capacitor C_(in), the detection electrode 131 and the programmable filter 151) is emulated by disposing the emulation circuit 150 to output the reference signal S_(ref) as a cancellation of the detection signal S_(ol), as shown in FIG. 4. The capacitance of the detection capacitor C_(in) is able to be decreased by subtracting the cancellation from the detection signal S_(ol). For example, the capacitance of the detection capacitor C_(in) is preferably smaller than 10 percent of capacitance of the self-capacitor C_(s). Therefore, the size of the control chip 100 is effectively decreased.

To make a difference between the touched differential detected signal S_(touch) and the non-touched differential detected signal S_(non) be more obvious, in some embodiments a gain circuit 153 is employed to amplify the differential detected signal S_(diff), wherein a gain of the gain circuit 153 is determined according to an analytical range of an analog-to-digital convertor (ADC) of the digital back end 16, but not limited thereto. As shown in FIG. 2, the difference between the touched differential detected signal S_(touch) and the non-touched differential detected signal S_(non), which are signals (i.e. differential detected signal) outputted by the gain circuit 153, is increased such that a touch event is easier to be identified. The anti-aliasing filter 154 filters the amplified differential detected signal and, as mentioned above, the anti-aliasing filter 154 is, for example, a low-pass filter.

Please refer to FIG. 3, it is another schematic block diagram of a capacitive touch device according to one embodiment of the present disclosure, wherein FIG. 3 further shows an implementation of the emulation circuit 150 and the programmable filter 151.

In some embodiments, the programmable filter 151 includes an input resistor R_(in) and an amplifying circuit 15A, wherein the detection capacitor C_(in), the self-capacitor C_(s), the input resistor R_(in) and the amplifying circuit 15A form a first filter circuit, and the emulation circuit 150 forms a second filter circuit. As mentioned above, the subtraction circuit 152 performs a differential operation on a detection signal S_(ol) outputted by the first filter circuit and a reference signal S_(ref) outputted by the second filter circuit to output a differential detected signal S_(diff), as shown in FIGS. 4A and 4B, wherein FIG. 4B shows a waveform of a differential detected signal S_(diff) of the detection signal S_(ol) and the reference signal S_(ref) shown in FIG. 4A.

In one embodiment, the amplifying circuit 15A includes an operational amplifier OP, a feedback resistor Rf and a compensation capacitor Cf. The feedback resistor Rf and the compensation capacitor Cf are connected between a negative input and an output of the operational amplifier OP. The input resistor R_(in) is coupled between a second end (i.e. the signal output) of the detection electrode 131 and the negative input of the operational amplifier OP. A first end (i.e. the signal input) of the detection electrode 131 is coupled to the detection capacitor C_(in). In this embodiment, a frequency response of the first filter circuit is indicated by equation (1) and the Bode diagram of FIG. 6, wherein the first filter circuit has two poles and a zero, which is located at 0.

(v _(out) /v _(in))=−(Rf/R _(in))x(s·C _(in) ·R _(in))/(1+s·Rf·Cf)x(1+s·R _(in) ·C _(s) +S·R _(in) ·C _(in))  (1)

As mentioned above, because an output of the emulation circuit 150 is used as a cancellation of the first filter circuit, the frequency response of the emulation circuit 150 is preferably similar to that of the first filter circuit, i.e. the frequency response of the emulation circuit 150 is determined according to a frequency response of the first filter circuit. In some embodiments, the two frequency responses are similar is referred to, for example, two poles of the emulation circuit 150 being close to two poles of the first filter circuit, but not limited thereto. For example, the two poles of the emulation circuit 150 are determined according to the two poles of the first filter circuit, and because the zero is not affected, only the pole frequencies are considered. For example, differences between pole frequencies of two poles of the emulation circuit 150 and frequencies of poles, which correspond to the two poles of the emulation circuit 150, of the second filter circuit is designed to be below 35 percent of the pole frequencies of the emulation circuit 150, and preferably to be below 20 percent. Although the two poles of the emulation circuit 150 are close to the two poles of the first filter circuit as much as possible, since it is difficult to precisely know the self-capacitor C_(s) of each detection electrode 131 in advance, the emulation circuit 150 is designed by estimation.

In one embodiment, the emulation circuit 150 includes an emulation detection capacitor C_(ref) _(_) _(in), an emulation self-capacitor C_(ref) _(_) _(s), an emulation input resistor R_(ref) _(_) _(in) and an emulation amplifying circuit 15B, and connections between the emulation detection capacitor C_(ref) _(_) _(in), the emulation self-capacitor C_(ref) _(_) _(s), the emulation input resistor R_(ref) _(_) _(in) and the emulation amplifying circuit 15B are arranged based on connections between the detection capacitor C_(in), the self-capacitor C_(s), the input resistor R_(in) and the amplifying circuit 15A to obtain a similar frequency response without particular limitations, e.g., having identical connections. That is, the emulation self-capacitor C_(ref) _(_) _(s) is used to emulate self-capacitor C_(s) of the detection electrode 131, the emulation detection capacitor C_(ref) _(_) _(in) is used to emulate the detection capacitor C_(in), the emulation input resistor R_(ref) _(_) _(in) corresponds to the input resistor R_(in), and the emulation amplifying circuit 15B corresponds to the amplifying circuit 15A. It should be mentioned that the circuit parameter of the emulation circuit 150 (i.e. RC value) is not necessary to be completely the same as the circuit parameter of the first filter circuit, as long as the frequency response of the emulation circuit 150 is similar to the frequency response of the first filter circuit, and the detection capacitor C_(s) is decreased without particular limitations.

The emulation amplifying circuit 15B also includes an operational amplifier OP′, an emulation feedback resistor R_(ref) _(_) _(f) and an emulation compensation capacitor C_(ref) _(_) _(f), wherein connections of elements in the emulation amplifying circuit 15B are arranged based on those of the amplifying circuit 15A without particular limitations, e.g., having identical connections. Therefore, a second filter circuit formed by the emulation circuit 150 also has a similar frequency response as the equation (1) and the Bode diagram of FIG. 6. The difference is that all element parameters of the emulation circuit 150 are predesigned. Accordingly, positions of two poles are adjustable by changing the element parameters, i.e. resistance and capacitance, of the emulation circuit 150.

Please refer to FIG. 5, it is a flow chart of an operating method of a capacitive touch device according to one embodiment of the present disclosure, including a self-capacitive mode (step S₅₁) and a mutual capacitive mode (step S₅₂). In this embodiment, the self-capacitive mode and the mutual capacitive mode is separately operated, e.g., firstly identifying an approaching object and/or a window of interest (WOI) using the self-capacitive mode and identifying a touch positions and/or a gesture using the mutual capacitive mode.

In the self-capacitive mode, the drive circuits 11 are respectively and electrically coupled to first ends of the drive electrodes via the detection capacitors C_(in), and the subtraction circuit 152 is respectively and electrically coupled to second ends of the drive electrodes. Meanwhile, because the subtraction circuit 152 receives a reference signal S_(ref) outputted by the emulation circuit 150 and the subtraction circuit 152 is electrically coupled to the second end of the drive electrodes via a programmable filter 151, the subtraction circuit 152 performs a differential operation on a detection signal S_(ol) outputted by the programmable filter 151 and the reference signal S_(ref) outputted by the emulation circuit 150 to output a differential detected signal S_(diff), as shown in FIGS. 4A and 4B. Then, a gain circuit 153 amplifies the differential detected signal S_(diff) to make a difference between a touched differential detected signal S_(touch) and a non-touched differential detected signal S_(non) be more significant, as shown in FIG. 2. Furthermore, in one embodiment, a touch event is identified by detecting detection signals outputted by a plurality of drive electrodes or a plurality of receiving electrodes to operate in a shorter scanning period.

In another embodiment, detection signals outputted by a plurality of drive electrodes and a plurality of receiving electrodes are detected to identify a window of interest (WOI) on the touch panel in a self-capacitive mode. Therefore, in the self-capacitive mode, the drive circuits 11 are respectively and electrically coupled to the first ends (i.e. signal inputs) of the receiving electrodes via the detection capacitors C_(in), and the subtraction circuit 152 is sequentially and electrically coupled to second ends (i.e. signal outputs) of the receiving electrodes. The window of interest is determined after identifying the drive electrode and the receiving electrode that sense an approaching object. As mentioned above, in the present disclosure the drive electrodes and the receiving electrodes are both belong to the detection electrodes 131 to generate mutual capacitors C_(m) therebetween.

In the mutual capacitive mode, the drive circuits 11 are respectively and electrically coupled to the first ends of the drive electrodes without passing the detection capacitors C_(in). For example in FIGS. 2 and 3, the drive circuits 11 bypass the detection capacitor C_(in) using a switch SW₁ and directly input the drive signal S_(d) to the detection electrode 131. Besides, the anti-aliasing filter 154 is respectively and electrically coupled to the second ends of the drive electrodes without passing the subtraction circuit 152. For example in FIGS. 2 and 3, the anti-aliasing filter 154 bypasses the subtraction circuit 152 (and the gain circuit 153) using another switch SW₂ to allow the detection signal S_(ol) outputted by the programmable filter 151 to be directly outputted to the anti-aliasing filter 154. The filter parameter of the anti-aliasing filter 154 is determined according to actual applications without particular limitation.

In the present disclosure, in the self-capacitive mode because signals sent to the detection lines do not pass resistors and capacitors of the panel, a phase difference between the reference line (i.e. emulation circuit) and the detection line is not obvious. Therefore, the reference signal S_(ref) is used as a cancellation to be subtracted from a detection signal.

It should be mentioned that, although the amplitude (or peak-to-peak value) of a non-touched differential detected signal S_(non) is shown to be larger than the amplitude (or peak-to-peak value) of a touched differential detected signal S_(touch) in FIG. 2, it is only intended to illustrate but not to limit the present disclosure. According to the parameter setting of the emulation circuit 150 (i.e. RC value), it is possible that the amplitude of the touched differential detected signal S_(touch) is larger than the amplitude of the non-touched differential detected signal S_(non).

It should be mentioned that although the amplitude (or peak-to-peak value) of a detection signal S_(ol) is shown to be larger than the amplitude (or peak-to-peak value) of a reference signal S_(ref) in FIG. 4A, it is only intended to illustrate but not to limit the present disclosure. According to the parameter setting of the emulation circuit 150 (i.e. RC value), it is possible that the amplitude of the reference signal S_(ref) is larger than the amplitude of the detection signal S_(ol).

As mentioned above, how to improve the touch sensitivity of a capacitive touch device is an important issue. Therefore, the present disclosure provides a capacitive touch device (FIGS. 1 to 3) and an operating method thereof (FIG. 5) that generate a cancellation by disposing an emulation circuit in a control chip to decrease a size of a capacitor in the control chip used in the self-capacitive mode and improve the touch sensitivity.

Although the disclosure has been explained in relation to its preferred embodiment, it is not used to limit the disclosure. It is to be understood that many other possible modifications and variations can be made by those skilled in the art without departing from the spirit and scope of the disclosure as hereinafter claimed. 

What is claimed is:
 1. A control chip for a touch panel, the touch panel comprising a detection electrode configured to form a self-capacitor, the control chip comprising: an input resistor configured to be coupled to an output end of the detection electrode; an amplifying circuit connected with the input resistor; and an emulation circuit configured to directly receive a drive signal and not connected to the output end of the detection electrode, wherein the input resistor and the amplifying circuit are configured to form a first filter circuit with the self-capacitor, the emulation circuit is configured to form a second filter circuit, and a frequency response of the second filter circuit is determined according to a frequency response of the first filter circuit.
 2. The control chip as claimed in claim 1, further comprising a subtraction circuit configured to perform a differential operation on a detection signal outputted by the first filter circuit and a reference signal outputted by the second filter circuit to output a differential detected signal.
 3. The control chip as claimed in claim 2, further comprising a gain circuit configured to amplify the differential detected signal.
 4. The control chip as claimed in claim 3, wherein the control chip is configured to identify a touch event according to a variation of peak-to-peak values of the amplified differential detected signal.
 5. The control chip as claimed in claim 1, further comprising a detection capacitor coupled to an input end of the detection electrode, wherein capacitance of the detection capacitor is smaller than 10 percent of capacitance of the self-capacitor.
 6. The control chip as claimed in claim 1, wherein the first filter circuit has two poles each has a pole frequency, the second filter circuit has two poles each has a pole frequency corresponding to the pole frequencies of the two poles of the first circuit, and differences between the pole frequencies of the two poles of the first filter circuit and that of the second filter circuit are lower than 35 percent of the pole frequencies of the first filter circuit.
 7. The control chip as claimed in claim 1, wherein the amplifying circuit comprises an operational amplifier, a feedback resistor and a compensation capacitor, the feedback resistor and the compensation capacitor are connected between a negative input and an output of the operational amplifier, and the input resistor is coupled between the output end of the detection electrode and the negative input of the operational amplifier.
 8. The control chip as claimed in claim 1, wherein the emulation circuit comprises: an emulation detection capacitor connected to a node and configured to directly receive the drive signal; an emulation self-capacitor connected between the node and ground; an emulation input resistor has a first end connected to the node; and an emulation amplifying circuit connected to a second end of the emulation input resistor.
 9. A control chip for a touch panel, the touch panel comprising a plurality of detection electrodes respectively configured to form a self-capacitor, the control chip comprising: an emulation circuit not connected to signal outputs of the detection electrodes and configured to directly receive a drive signal and output a reference signal; a plurality of programmable filters respectively coupled to the signal outputs of the detection electrodes; and a subtraction circuit, directly connected to the emulation circuit, and configured to be sequentially coupled to the programmable filters in a self-capacitive mode, and perform a differential operation on the reference signal outputted by the emulation circuit and a detection signal outputted by the coupled programmable filter to output a differential detected signal.
 10. The control chip as claimed in claim 9, further comprising a gain circuit configured to amplify the differential detected signal.
 11. The control chip as claimed in claim 10, wherein the control chip is configured to identify a touch event according to a variation of peak-to-peak values of the amplified differential detected signal.
 12. The control chip as claimed in claim 9, wherein each programmable filter comprises an input resistor and an amplifying circuit.
 13. The control chip as claimed in claim 12, further comprising a plurality of detection capacitors configured to be respectively coupled to signal inputs of the detection electrodes, wherein each of the programmable filters and the detection capacitors are configured to form a first filter circuit with the self-capacitor of the coupled detection electrode.
 14. The control chip as claimed in claim 13, wherein the emulation circuit is configured to form a second filter circuit, and a frequency response of the second filter circuit is determined according to a frequency response of the first filter circuit.
 15. The control chip as claimed in claim 13, wherein capacitance of the detection capacitors is smaller than 10 percent of capacitance of the self-capacitor.
 16. The control chip as claimed in claim 13, wherein the detection capacitors are respectively coupled to the signal inputs of the detection electrodes via a plurality of first switches, and the subtraction circuit is coupled to the programmable filters respectively via a plurality of second switches.
 17. An operating method of a control chip for a touch panel, the touch panel comprising a plurality of drive electrodes and a plurality of receiving electrodes extending along different directions, and the control chip comprising an emulation circuit, a plurality of detection capacitors, a subtraction circuit and an anti-aliasing filter, the operating method comprising: respectively coupling, in a self-capacitive mode, a first drive signal to first ends of the drive electrodes via the detection capacitors and respectively coupling the subtraction circuit to second ends of the drive electrodes; directly inputting, in the self-capacitive mode, another drive signal to the emulation circuit, which is not connected to the second ends of the drive electrodes, to output a reference signal; and respectively coupling, in a mutual capacitive mode, the first drive signal to the first ends of the drive electrodes without passing the detection capacitors, and respectively coupling the anti-aliasing filter to second ends of the receiving electrodes without passing the subtraction circuit.
 18. The operating method as claimed in claim 17, further comprising: respectively coupling, in the self-capacitive mode, the first drive signal to first ends of the receiving electrodes via the detection capacitors, and respectively coupling, in the self-capacitive mode, the subtraction circuit to the second ends of the receiving electrodes.
 19. The operating method as claimed in claim 17, wherein the control chip further comprises a plurality of programmable filters, the subtraction circuit is electrically coupled to the second ends of the drive electrodes via the programmable filters respectively, and the operating method further comprises: performing a differential operation on a detection signal outputted by the coupled programmable filter and the reference signal outputted by the emulation circuit to output a differential detected signal; amplifying the differential detected signal; and identifying a touch event according to a variation of peak-to-peak values of the amplified differential detected signal.
 20. The operating method as claimed in claim 19, wherein the programmable filters and the detection capacitors form a first filter circuit with the self-capacitors of the drive electrodes, the emulation circuit forms a second filter circuit, and a frequency response of the second filter circuit is determined according to a frequency response of the first filter circuit. 